Comment 16 for bug 1372149

This mean he probably used extension hg-git. I had the same issue with export. How i discovered you can't use use hg-git higher than version 0.6.1.

In my case i use mercurial->git->launchpad. So for restoring my repository i completely deleted it and made export with hg-git v0.6.1. Export works until now without errors.